We propose to develop human cell lines expressing rat cytochrome P450 cDNAs. Two rat cytochrome P450 cDNAs, encoding P450IIB1 and P450IID1, will be transfected into the AHH-1 TK+/- line of human lymphoblastoid cells. Vectors containing the Epstein Barr virus origin of replication will be used in this transfection. Recombinant cell populations will be isolated and specific cytochrome P450 catalyzed reactions will be measured in recombinant and control cell populations. The recombinant cell lines will also be used in gene mutation assays. Promutagens known to be activated by the specific P450 forms will be tested. The eventual goal of this program is to develop a panel of cell lines expressing rat cytochrome P450s. This panel can be used to analyze rat foreign compound metabolism with the ability to relate metabolite formation with the induction of genotoxicity in the same cell line. Additional applications include analysis of strain or sex specific cytochrome P450s and also comparison to human P450s in the same cell system.